Scientists have found that Ilamas' blood can help fight against HIV/AIDS in a new study.
After initial disappointment that HIV vaccine candidates were unable to elicit neutralizing antibodies, researchers found that some HIV-infected individuals did produce them. The current challenge is therefore to find safe and effective vaccine formulations (as opposed to HIV infection) that trigger the development of neutralizing antibodies that can recognize and prevent infection with all or most circulating HIV subtypes.
Llamas are a notable exception when it comes to neutralizing antibodies, as besides the common four-chain antibodies they also produce smaller ones made up of only two of the four chains. Robin Weiss, an HIV expert, and Theo Verrips, a llama antibody expert, therefore started working with this unconventional research animal.
Laura McCoy (working with Weiss at University College London, UK) led an international group of researchers to test immunization protocols and the resulting immune response in llamas. Having previously identified one particular HIV neutralizing llama antibody, for this study the researchers immunized two additional llamas and identified a total of three new neutralizing antibodies. The four HIV neutralizing llama antibodies target different parts of the CD4-binding site of the virus, and the researchers could show that when used in combination, rather than interfering with each other, they are more potent and can neutralize all of the 60 different HIV strains tested.
The results suggest that the neutralizing antibodies were not part of the pre-immunization repertoire, nor were they detectable after the first vaccination round. Rather, they were generated as immune cells repeatedly encountered the vaccine and responded by maturing specific antibodies that can recognize it.
Their results, they say, "show that immunization can induce potent and broadly neutralizing antibodies in llamas with features similar to human antibodies, and provide a framework to analyze the effectiveness of immunization protocols."
The study is published in PLOS Pathogens.